It sounds like you're getting out either "Dark Stuff" or "Black Stuff". Depending on who you ask, that's what happens when you put the ingredients for a dark brew in (1:2:3 ratio of wheat to hops to water, I think) but tap and drain it before it really starts to ferment, or it's what you get out of a booze barrel when you put in too many solids with too little water. Either way, they're both a useless drink, unless you enjoy poison and want to impress your spider friends. Fermentation takes between 2 hours (real hours) and 12+ hours for beer, and up to a day (again, a real day, not a minecraft day) for good rum.

You can vary the result even for very young (no fermentation) brews by altering the ratio of wheat, hops, water. You can get even more variation by leaving it fermenting for several Minecraft days or weeks to let the character and alcohol develop – just like a real-life homebrew.

The IC2 Wiki has a decent starter guide to beer and rum brewing on the Empty Booze Barrel page, including many of the ratios and the beer styles that they give. The effects of each is left up to the player to discover.

Note that if you filled the barrel up quite a bit (many multiples of the wheat:hops:water mix), you will get out as many drinks as you put in water cells. If you have a substantially-full barrel, you can tap it, fill a mug and try it, and then take the tap out to let the rest continue fermenting. You can set up a few barrels in a cellar so you can start a variety of mixes at once to see what they do as they age. This is a good way to experiment to find out what kind of beer (and its effects) you prefer. Beware of unfermented drinks though – they tend to have strictly harmful effects, and some of it can outright kill you. There is a long thread about brewing recipes on the IC2 forums that is an attempt to collect research on recipes and their effects.